Predicting Fetal Weight by Ultrasonography Using Hadlock Formula 1

Abstract

Background: Accurate fetal weight estimations by ultrasound are essential in determining the method and time of delivery. Hadlock formulas have been proposed for providing fetal weight estimations, including Hadlock 1, Hadlock 2, Hadlock 3, and Hadlock 4. Because none of the formulas have been verified, it is unknown which one can be best applied to the Saudi population. This study aims to determine the validity of the Hadlock formula 1 for EFW by using ultrasonography. Methods and Results: The study sample was 198 women with singleton pregnancies with gestational ages between 37 and 41 weeks, admitted for ultrasound evaluation. The FW was estimated by ultrasound using the Hadlock formula 1. After the ultrasound EFW, we followed up with the pregnant women within three days (from ultrasound scan to delivery date) and measured actual BW. The study found that the mean BW was 3179±387 g, ranging from 2500 g to 4290 g. The mean ultrasound EFW was 3055±378 g, ranging from 2500 g to 4100 g. The difference between the mean ultrasound EFW and actual BW (123.81±107.95 g) was significant (P=0.0014).The formula for prediction of birth weight is BW=0.9831EFW by ultrasound±175.55g. In addition, a significantly positive correlation was found between ultrasound EFW and BW (r=0.961, P=0.000). Conclusion: The significantly positive correlation between EFW by ultrasound and BW indicates that the Hadlock formula 1 for predicting FW is accurate, valid, and effective in the research environment.

Keywords

• birth weight
• hadlock formula
• estimated fetal weight
• ultrasonography